Historically, mayors in Mexico were limited to a single 3-year term and could not run for reelection. In 2014, Mexico amended the Constitution, extending the term limit to two terms. When will be the first mayoral election where this takes effect and incumbents can run for reelection?
In June, 2017, elections will be held in the state of Coahuila, where 38 mayor offices will be disputed. Those elected to this offices will be the first ellegible to run for a second term since the Mexican revolution ended in 1920.
It should be noted that the Mexican Revolution started in 1910, to prevent the reelection of president Porfirio Díaz, and that to this day, the official motto of the United Mexican States is sufragio efectivo, no reelección literally effective suffrage, no reelection which was the fundamental tenet of this conflict, and is printed as the closing line of all official federal documents, be it an internal government memo or a major law decree.
If only Mexican politics were so simple! As it happens, the reformed statute demands that in order to run for a second term, such officials must effectively leave office at least 6 months prior to the elections on which they intend to run as incumbents, the spirit of the law being that this would ensure that the incumbents can't use public resources to finance their reelection campaign.
However, this election coincides with an adjustment of the State of Coahuila's electoral calendar so as to align the date of elections for mayor, with the elections for state governor and legislature, to optimize resources organizing a single state-wide election
This requires elections for mayor be held again in June 2018. creating a special one-time "short term" of one year for mayors elected in 2017.
This creates a perhaps unforseen situation in which any mayor elected during the June 2017 and aspires to run either for reelection to the same office or a higher office at the state legislature, would only be able to serve for 5 days, since they would be inaugurated on January 1, and should leave office by January 6 in order to be ellegible to run for office in the June 2018 election
The more logical alternative of extending the terms of the current mayors would be unconstitutional, since they were elected for a term of 3 years only.
Politicians that run for elected office in order to use it as a stepping stone to an higher office thus usually resigning their office before finishing their terms is quite common in Mexican politics, and it's generally frowned upon and those who plan on using this strategy don't reveal their intention to do so, and they are derisively called chapulines, literally grasshoppers (this note will make the referring article a bit more understandable for those unfamiliar with Mexican electoral slang